Zamora-Sánchez et al. BMC Geriatrics (2021) 21:243 https://doi.org/10.1186/s12877-021-02186-x RESEARCH ARTICLE Open Access Convergent and discriminative validity of the Frail-VIG index with the EQ-5D-3L in people cared for in primary health care Juan-José Zamora-Sánchez1,2, Edurne Zabaleta-del-Olmo1,3,4,5*, Vicente Gea-Caballero6,7, Iván Julián-Rochina8,9, Gemma Pérez-Tortajada10 and Jordi Amblàs-Novellas11 Abstract Background: The Frail-VIG frailty index has been developed recently. It is an instrument with a multidimensional approach and a pragmatic purpose that allows rapid and efficient assessment of the degree of frailty in the context of clinical practice. Our aim was to investigate the convergent and discriminative validity of the Frail-VIG frailty index with regard to EQ-5D-3L value. Methods: We carried out a cross-sectional study in two Primary Health Care (PHC) centres of the Catalan Institute of Health (Institut Català de la Salut), Barcelona (Spain) from February 2017 to January 2019. Participants in the study were all people included under a home care programme during the study period. No exclusion criteria were applied. We used the EQ-5D-3L to measure Health-Related Quality of Life (HRQoL) and the Frail-VIG index to measure frailty. Trained PHC nurses administered both instruments during face-to-face assessments in a participant’s home during usual care. The relationships between both instruments were examined using Pearson’s correlation coefficient and multiple linear regression analyses. Results: Four hundred and twelve participants were included in this study. Frail-VIG score and EQ-5D-3L value were negatively correlated (r = − 0.510; P < 0.001). Non-frail people reported a substantially better HRQoL than people with moderate and severe frailty. EQ-5D-3L value declined significantly as the Frail-VIG index score increased. Conclusions: Frail-VIG index demonstrated a convergent validity with the EQ-5D-3L value. Its discriminative validity was optimal, as their scores showed an excellent capacity to differentiate between people with better and worse HRQoL. These findings provide additional pieces of evidence for construct validity of the Frail-VIG index. Keywords: Frailty, Health status, Primary health care, Psychometrics, Validation studies as topic Background construct validity are two types of validity. Criterion Validity is defined as “the degree to which an instrument validity is applicable when there is the gold standard for truly measures the construct(s) it purports to measures” the construct that is measured, it refers to the degree to [1]. Validation is a continuous process and different which the scores of a measurement instrument are an forms of validation can be applied. Criterion validity and adequate reflection of a gold standard [1, 2]. By contrast, construct validity is applicable when there is no gold * Correspondence: ezabaleta@idiapjgol.org 1 standard, it refers to the degree to which the scores of a Gerència Territorial de Barcelona, Institut Català de la Salut, Gran Via Corts measurement instrument are consistent with the avail- Catalanes 587 àtic, 08007 Barcelona, Spain 3 Fundació Institut Universitari per a la recerca a l’Atenció Primària de Salut able knowledge about the construct [1, 2]. Jordi Gol i Gurina (IDIAPJGol), Barcelona, Spain Full list of author information is available at the end of the article © The Author(s). 2021 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Zamora-Sánchez et al. BMC Geriatrics (2021) 21:243 Page 2 of 7 On the other hand, frailty is defined as “a clinical state Methods in which there is an increase in an individual’s vulner- Study design ability to develop negative health-related events (includ- We conducted a cross-sectional study on measurement ing disability, hospitalizations, institutionalizations, and properties. death) when exposed to endogenous or exogenous stressors” [3]. It is a complex and multidimensional con- Setting and participants cept for which there are numerous and multiple oper- The study was carried out in two PHC centres of the ational definitions. This fact has contributed to the lack Catalan Institute of Health (Institut Català de la Salut), of an accepted gold standard [3, 4]. As a result, most Barcelona (Spain) from February 2017 to January 2019. frailty measurement instruments assess their validity by In these centres, people who cannot visit the centre for analysing the degree of consistency of their scores with PHC services are included under a home care different hypotheses about their relationship with other programme and are cared at-home by PHC centre’s pro- instruments or the differences between relevant groups. fessionals. Participants in the study were all people in- In other words, hypothesis testing for construct validity cluded under a home care program during the study studies is carried out because of the difficulty in asses- period. No exclusion criteria were applied. sing criterion validity. A new frailty index, the Frail-VIG index, has been developed recently [5, 6]. It is an instrument with a Variables and data measurements multidimensional approach and a pragmatic purpose We used the EQ-5D-3L to measure HRQoL which is that allows rapid and efficient assessment of the degree one of the most widely used measurement instruments of frailty in the context of clinical practice. This meas- [11–13]. It is a generic measurement instrument because urement instrument has shown to have an optimal it measures HRQoL in a way that can be used across dif- capacity to predict two-year mortality (Area Under ferent types of patients, health conditions, and treat- Curve 0.85) [6]. The relationship of their scores with ments. This instrument comprises two parts. The first those of the Clinical Frailty Scale [7] has been evaluated part consists of five dimensions: mobility, self-care, usual in a cross-sectional study and a strong positive correl- activities, pain/discomfort, and anxiety/depression. Each ation (r = 0.706) has been established [8]. All of these dimension has three levels: no problems, some problems, studies have been conducted in an inpatient hospital and extreme problems. Unique health status is defined setting and there have been no studies in primary health by combining a level of each of the five dimensions care (PHC) settings. resulting in a five-digit number, with 11,111 reflecting Previous research suggests an association between frailty the best possible health status and 33,333 the worst. The and worse quality of life, but its findings are mixed and in- second part of the instrument is the EQ VAS which consistent. However, recent systematic reviews show a comprises a visual analogue scale from 0 (the worst consistent negative association between frailty and quality health imaginable) to 100 (the best health imaginable). of life among community-dwelling people [9, 10]. Besides, EQ-5D-3L is designed for self-completion by respon- the validity of a measuring instrument does not reside in dents, but several other modes of administration (inter- the instrument itself but in how it is used and hence de- view administered, face-to-face interview, or telephone pends on its appropriateness to the target population and interview) are also possible. Existing research has estab- the specific context of administration [2]. Therefore, a lished that self-completion and assisted completion pro- good approach to further developing evidence of the valid- duce equivalent scores overall and therefore both ity of the Frail-VIG index would mean to analyse the rela- methods can be used [14, 15]. For the present study we tionship of its scores with those of another instrument used the Spanish face-to-face interview version as a large that measures the quality of life (both instruments admin- majority of the participants were unable to read and istered in the context of PHC). write [16]. Consequently, we carried out this study in a PHC set- Frailty was measured using the original Spanish version ting to investigate the convergent and discriminative val- of Frail-VIG index. It is composed of 22 items that evalu- idity of the Frail-VIG index regard to health-related ate 25 deficits based on the comprehensive geriatric as- quality of life (HRQoL) measured by the EQ-5D three- sessment [5, 6]. It is constructed using only variables level version (EQ-5D-3L). Concerning convergent valid- recorded during the usual clinical evaluation process. The ity, we hypothesised that the relationship of scores be- value of the index is obtained from the sum of the identi- tween instruments was moderate to strong and negative. fied deficits divided by 25, the total number of potential With regard to discriminative validity, we hypothesised deficits, so the higher the presence of deficits the higher that non-frail people would have higher scores on the score in the index. Likewise, different index cut-off HRQoL than frail people. points have been established that distinguish between four Zamora-Sánchez et al. BMC Geriatrics (2021) 21:243 Page 3 of 7 Table 1 General characteristics of participants overall and by frailty states. Values are absolute frequencies (percentages) unless stated otherwise Frailty states according to Frail-VIG index Total Non- Mild Moderate Severe (n = frailty frailty frailty frailty 412) < 0.20 0.20–035 0.36–050 > 0.50 (n = 12) (n = 116) (n = 191) (n = 93) Variable Description Age, mean (SD) 88.0 (8.1) 86.7 (8.0) 88.8 (7.4) 88.1 (8.2) 86.8 (8.8) Female 282 (68,4) 9 (75.0) 81 (69.8) 126 (66.0) 66 (71.0) Health-related quality of life EQ-5D-3L value, mean (SD) 0.30 (0.23) 0.48 (0.19) 0.42 (0.20) 0.29 (0.22) 0.13 (0.15) Domains and variables of Frail-VIG frailty index Functional domain IADLs: Money Needs help managing financial matters (bank, shops, 350 (85.0) 5 (41.7) 79 (68.1) 173 (90.6) 93 (100.0) management or restaurants) IADLs: Needs help using the telephone 132 (32.0) 0 (0.0) 4 (3.4) 58 (30.4) 70 (75.3) Telephone use IADLs: Needs assistance in preparing or administering 304 (73.8) 0 (0.0) 51 (44.0) 161 (84.3) 92 (98.9) Medication medications management ADLs: Barthel No dependency (BI > = 95) 6 (1.5) 1 (8.3) 3 (2.6) 2 (1.0) 0 (0.0) index (BI) Mild-moderate dependency (BI from 90 to 65) 143 (34.7) 11 (91.7) 79 (68.1) 51 (26.7) 2 (2.2) Moderate-severe dependency (BI from 60 to 25) 175 (42.5) 0 (0.0) 33 (28.4) 111 (58.1) 31 (33.3) Absolute dependency (BI <=20) 88 (21.4) 0 (0.0) 1 (0.9) 27 (14.1) 60 (64.5) Nutritional domain Malnutrition Weight loss > = 5% in the las 6 months 70 (17.0) 0 (0.0) 10 (8.6) 34 (17.8) 26 (28.0) Cognitive domain Degree of No cognitive impairment 198 (48.1) 12 (100.0) 90 (77.6) 86 (45.0) 10 (10.8) cognitive impairment Mild-moderate cognitive impairment (equivalent to 171 (41.5) 0 (0.0) 26 (22.4) 93 (48.7) 52 (55.9) GDS < =5) Severe-very severe cognitive impairment (equivalent 43 (10.4) 0 (0.0) 0 (0.0) 12 (6.3) 31 (33.3) to GDS > =6) Emotional domain Depressive Need for antidepressant medication 158 (38.3) 0 (0.0) 25 (21.6) 82 (42.9) 51 (54.8) syndrome Insomnia/ Frequent need for benzodiazepines or other psychiatric 226 (54.9) 4 (33.3) 55 (47.4) 104 (54.5) 63 (67.7) anxiety drugs with a sedative effect for insomnia/anxiety Social domain Social Do health care professionals perceive the presence of 212 (51.5) 4 (33.3) 69 (59.5) 93 (48.7) 46 (49.5) vulnerability social vulnerability? Geriatric syndromes Delirium Presence of delirium and/or behaviour disorder requiring 119 (28.9) 0 (0.0) 8 (6.9) 48 (25.1) 63 (67.7) antipsychotic drugs in the last6 months Falls In the last 6 months, ≥2 falls or hospitalization due to a fall. 112 (27.2) 0 (0.0) 21 (18.1) 56 (29.3) 35 (37.6) Ulcers Presence of ulcer (pressure or vascular, any grade) 85 (20.6) 0 (0.0) 9 (7.8) 39 (20.4) 37 (39.8) Polypharmacy Taking ≥5 drugs 365 (88.6) 8 (66.7) 91 (78.4) 178 (93.2) 88 (94.6) Dysphagia Difficulty swallowing when eating or drinking? Presence of 75 (18.2) 0 (0.0) 2 (1.7) 24 (12.6) 49 (52.7) aspiration respiratory infections during the last 6 months? Severe symptoms Pain Need for ≥2 conventional analgesics and/or strong opioids 87 (21.1) 3 (25.0) 15 (12.9) 49 (25.7) 20 (21.5) for pain control Dyspnoea Basal dyspnoea impeding the ability to leave the house 19 (4.6) 0 (0.0) 3 (2.6) 10 (5.2) 6 (6.5) and/or opioids are frequently needed Zamora-Sánchez et al. BMC Geriatrics (2021) 21:243 Page 4 of 7 Table 1 General characteristics of participants overall and by frailty states. Values are absolute frequencies (percentages) unless stated otherwise (Continued) Frailty states according to Frail-VIG index Total Non- Mild Moderate Severe (n = frailty frailty frailty frailty 412) < 0.20 0.20–035 0.36–050 > 0.50 (n = 12) (n = 116) (n = 191) (n = 93) Diseases Cancer Active cancer 36 (8.7) 0 (0.0) 4 (3.4) 24 (12.6) 12 (12.9) Respiratory Presence of any type of chronic respiratory disease (COPD, 116 (28.2) 1 (8.3) 23 (19.8) 61 (31.9) 31 (33.3) restrictive lung disease...) Cardiac Presence of any type of chronic heart disease (heart failure, 248 (60.2) 2 (16.7) 57 (49.1) 124 (64.9) 65 (69.9) ischemic cardiomyopathy, arrhythmia Neurological Presence of any type of neurodegenerative disease (Parkinson, 151 (36.7) 0 (0.0) 24 (20.7) 75 (39.3) 52 (55.9) ALS...) or a history of stroke (ischemic or haemorrhagic) Digestive Presence of any type of chronic digestive disease (chronic liver 39 (9.5) 1 (8.3) 8 (6.9) 22 (11.5) 8 (8.6) disease, cirrhosis, chronic pancreatitis, inflammatory bowel disease, ... Renal Presence of chronic renal failure (GFR < 60) 204 (49.5) 4 (33.3) 57 (49.1) 102 (53.4) 41 (44.1) ADLs Activities of Daily Living, ALS Amyotrophic lateral sclerosis, COPD Chronic Obstructive Pulmonary Disease, GDS Global deterioration scale, GFR Glomerular Filtration Rate, IAVDs Instrumental Activities of Daily Living, SD Standard deviation degrees of frailty: non-frailty, < 0.20; mild, 0.20 to 0.35; detect possible problems and to introduce improvement moderate, 0.36 to 0.50 and severe > 0.50 [6]. strategies. After this pilot test, no changes in the Researchers developed an instruction manual for the procedure were necessary. administration of instruments. Trained PHC nurses administered both instruments during face-to-face Statistical methods assessments in a participant’s home during usual care. We applied a scoring algorithm based on the These interviews had an average duration of 30 min. A Spanish population to convert EQ-5D-3L states into pilot test with 20 participants was also carried out to a single summary value [13, 17]. This value is Table 2 Prevalence of the 10 most frequently observed EQ-ED-3 L profiles and frequency of reporting of the worst possible profile according to frailty state (these were the 10 profiles of 63.1% (n = 260) of the study population (the most frequent profiles in each of the frailty states are highlighted in bold). Profiles, Total Frailty states according to Frail-VIG index n (%) (n = Non-frailty Mild frailty Moderate frailty Severe frailty 412) < 0.20 0.20–035 0.36–050 > 0.50 (n = 12) (n = 116) (n = 191) (n = 93) Top 10 profiles 33322 62 (15.0) 0 (0.0) 4 (3.4) 24 (12.6) 34 (36.6) 22222 60 (14.6) 1 (8.3) 27 (23.3) 26 (13.6) 6 (6.5) 23322 29 (7.0) 0 (0.0) 2 (1.7) 18 (9.4) 9 (9.7) 22221 23 (5.6) 1 (8.3) 12 (10.3) 9 (4.7) 1 (1.1) 22211 22 (5.3) 1 (8.3) 7 (6.0) 14 (7.3) 0 (0.0) 22212 20 (4.9) 1 (8.3) 6 (5.2) 10 (5.2) 3 (3.2) 33311 13 (3.2) 0 (0.0) 0 (0.0) 9 (4.7) 4 (4.3) 22322 12 (2.9) 0 (0.0) 6 (5.2) 6 (3.1) 0 (0.0) 33321 12 (2.9) 0 (0.0) 0 (0.0) 3 (1.6) 9 (9.7) 21221 7 (1.7) 2 (16.7) 4 (3.4) 1 (0.5) 0 (0.0) Worst possible 33333 4 (1.0) 0 (0.0) 0 (0.0) 2 (1.0) 2 (2.2) Each digit of profile label corresponds to one of the five dimensions of the EQ-5D-3L (from left to right): Mobility, Self-Care, Usual activities, Pain and discomfort, and Anxiety and depression Level 1, no problems; Level 2, moderate problems, and level 3, extreme problems Zamora-Sánchez et al. BMC Geriatrics (2021) 21:243 Page 5 of 7 “attached to an EQ-5D profile according to a set of Table 3 EQ-5D-3L value (from “0”, “a state as bad as being weights that reflect, on average, people’s preferences dead” to “1”,“full health”) for the total study population and the about how good or bad the state is” [18] and ranges seven groups based on their Frail-VIG score (from “0”, “absence from 1 (full health) to 0 (a state as bad as being of frailty” to “1”, “severe frailty”) death), although there are negative values for the EQ-5D-3L value value, corresponding to those states of health that Frail-VIG index score n Mean (SD) Median (25th–75th) are rated as worse than death. This value is often 0–0.15 4 0.55 (0.21) 0.62 (0.32–0.69) used in economic evaluations, but it can also be 0.16–0.25 50 0.49 (0.17) 0.54 (0.32–0.60) used to describe the health of a population or the 0.26–0.35 74 0.38 (0.20) 0.49 (0.22–0.54) severity of disease among patients [19]. 0.36–0.45 150 0.31 (0.23) 0.23 (0.12–0.54) We calculated central tendency and dispersion measures for the quantitative variables. For categor- 0.46–0.55 72 0.21 (0.20) 0.12 (0.04–0.33) ical variables, we estimate absolute and relative 0.56–065 55 0.12 (0.13) 0.09 (0.04–0.15) frequencies. The relationships between the Frail-VIG 0.66–1 7 0.05 (0.07) 0.04 (0.04–0.12) index and the EQ-5D-3L value were examined using Total 412 0.30 (0.23) 0.23 (0.09–0.49) Pearson’s correlation coefficient and multiple linear ANOVA (F = 22.887; degrees of freedom = 6; P < 0.001 regression analyses. Correlation coefficients of ≤0.29 EQ-5D-3L value ranged from − 0.08 to 1 were considered weak, 0.30–0.49 as low, 0.50–0.69 as moderate, and ≥ 0.70 was considered strong Furthermore, its discriminative validity was optimal, as correlation [20]. To examine whether non-frail their scores showed an excellent capacity to differentiate people had higher scores on HRQoL than frail between people with better and worse HRQoL. people, a one-way ANOVA was conducted, with Consistent with the literature, this research found that frailty status as the independent variable and the HRQoL and frailty were negatively associated among EQ-5D-3L value as the dependent variable. We used community-dwelling older people [9, 10]. Studies on the statistical software IBM SPSS Statistics version other cumulative deficit models of frailty have also found 24 for all analyses. a negative relationship between the frailty state and the scores of instruments measuring HRQoL, well-being and Results life satisfaction [9, 10, 21–23]. However, the results of Four hundred and twelve participants were included in this study show that not only is the frailty state associ- this study. Table 1 shows their general characteristics ated with a worse HRQoL but also that there is a linear and frailty status according to the Frail-VIG index association between both indexes (Frail-VIG index and scores. EQ-5D-3L value). Hypothesis testing is an ongoing Table 2 describes the 10 most frequent EQ-ED-3 L process, so the more hypotheses are tested the more evi- profiles according to frailty status. The worst of these dence is generated for construct validity [24]. Therefore, profiles was most prevalent among people with severe this research supports evidence from previous studies frailty, while the best was more frequent among non- carried out in the hospital setting on the construct valid- frailty people. ity of the Frail-VIG index [6, 8]. Pearson’s correlation coefficient between Frail-VIG This study has several strengths. Most validation index and EQ-5D-3L value was negative and moderate studies of measurement instruments of frailty in (r = −0.510; P < 0.001). After adjusting for age and sex community-dwelling people focus on demonstrating variables, the multiple linear regression model revealed their predictive potential for adverse outcomes or re- that Frail-VIG index independently correlated with EQ- source use, such as disability, institutionalisation or 5D-3L value (B = -0.945; 95% Confidence Interval, hospital admissions [25–27]. In contrast, studies that −1.098 to − 0.791; R2 = 0.287). As you can see from analyse their relationship to more positive outcomes Table 1, non-frail people reported a substantially better such as HRQoL are less common [10, 28]. Likewise, the HRQoL than people with moderate and severe frailty use of the Frail-VIG index in primary care has been people. Likewise, closer inspection of Table 3 shows that poorly studied, and this is one of the first studies to the EQ-5D-3L value declined significantly as the Frail- analyse its construct validity in this care setting. How- VIG index score increased. ever, some limitations exist. The representativeness of non-frailty people is very low (12 people), probably be- Discussion cause the study population were people in a home-care In this study, involving people cared at-home by PHC programme. A greater representation of this population professionals, we found that the Frail-VIG index demon- might have influenced the Frail-VIG index’s discrimina- strated convergent validity with the EQ-5D-3L value. tive validity observed. In addition, we used the EQ-5D Zamora-Sánchez et al. BMC Geriatrics (2021) 21:243 Page 6 of 7 values for this assessment of the measurement proper- interpretation of data, and the critical review of the manuscript. All authors ties of the Frail-VIG index instead of other values such read and approved the final manuscript. as the EQ VAS. The EQ VAS can be considered a Funding measure closer to the patient’s perspective than the This research was supported by the Health Department grant number EQ-5D values [29]. Nevertheless, as Devlin and Parkin (SLT008/18/00011) from the Generalitat of Catalunya (Spain) and by a grant from the Territorial Management of Barcelona of the Institut Català de la point out [19], being able to summarise and represent a Salut (Catalan Institute of Health) to the first author (JJZS) in the 2018 health profile with a single value has important advan- edition. The funders had no role in review design, decision to publish, or tages, including simplifying statistical analyses. On the preparation of this manuscript. other hand, both the EQ-5D values and the EQ VAS Availability of data and materials are able to discriminate between the quality of life of The data that support the findings of this study are available from the most groups of individuals with different socio- corresponding author, [EZO], upon reasonable request. demographic factors, and those with or without clinical Declarations conditions [30]. Furthermore, some studies [31] and experts in the field of psychometrics [32] report that Consent to publication older people experience difficulties in understanding Not applicable. and completing direct estimation methods, such as the Ethics approval and consent to participate visual analogue scale. For all these reasons, we chose We followed the guidelines established by the COnsensus-based Standards the EQ-5D values to carry out this psychometric study. for the selection of health Measurement INstruments (COSMIN) [35] and the STrengthening the Reporting of OBservational studies in Epidemiology People living with frailty risk experiencing a decline (STROBE) for cross-sectional studies [36]. This research and collection of data in their quality of life [9, 10, 33]. The findings of this used were approved by the IDIAPJGol Clinical Research Ethics Committee study suggest that the interventions aimed at decreas- (registration number P17/150). All data were collected with informed consent from participants before beginning the interviews. ing frailty could have the added benefit of improving the HRQoL. PHC professionals are naturally posi- Competing interests tioned to identify frailty early and to implement inter- The authors declare that they have no competing interests. ventions that prevent related adverse effects on the Author details most vulnerable people [4]. Moreover, the assessment 1 Gerència Territorial de Barcelona, Institut Català de la Salut, Gran Via Corts of frailty in PHC settings requires tools that are not Catalanes 587 àtic, 08007 Barcelona, Spain. 2School of Nursing, Universitat de Barcelona, Barcelona, Spain. 3Fundació Institut Universitari per a la recerca a time consuming as well as valid and reliable which is l’Atenció Primària de Salut Jordi Gol i Gurina (IDIAPJGol), Barcelona, Spain. way the Frail-VIG index could provide a useful and 4 Universitat Autònoma de Barcelona, Bellaterra, Cerdanyola del Vallès, Spain. 5 appropriate tool for this care setting [34]. Nursing Department, Faculty of Nursing, Universitat de Girona, Girona, Spain. 6Nursing school “La Fe”, Valencia, Spain. 7GREIACC Research Group, Instituto de Investigación Sanitaria La Fe, Valencia, Spain. 8Nursing Conclusions Department, Universitat de Valencia, Valencia, Spain. 9Fragilidad y Deterioro This study has identified a negative moderate correlation Cognitivo (FROG) Research Group, Universitat de Valencia, Valencia, Spain. 10 Primary care centre “Fondo”, Gerència Territorial Metropolitana Nord, between the Frail-VIG index and the EQ-5D-3L values. Institut Català de la Salut, Santa Coloma de Gramenet, Spain. 11Central It has also shown that the Frail-VIG index was able to Catalonia Chronicity Research Group (C3RG), Centre for Health and Social discriminate significantly home-dwelling older people Care Research (CESS), Universitat de Vic – University of Vic-Central University of Catalonia (UVIC-UCC), 08500 Vic, Spain. according to their HRQoL. These findings provide add- itional pieces of evidence for construct validity of the Received: 3 November 2020 Accepted: 30 March 2021 Frail-VIG index. Further research is needed on this new measurement instrument to determine its suitability for References screening and preventing adverse effects of frailty in 1. Mokkink LB, Terwee CB, Patrick DL, Alonso J, Stratford PW, Knol DL, et al. PHC settings. The COSMIN study reached international consensus on taxonomy, terminology, and definitions of measurement properties for health-related Abbreviations patient-reported outcomes. J Clin Epidemiol. 2010;63(7):737–45. ADLs: Activities of Daily Living; ALS: Amyotrophic Lateral Sclerosis; 2. DeVellis RF. Validity. In: Scale development theory and applications. 4th ed. COPD: Chronic Obstructive Pulmonary Disease; GDS: Global Deterioration Los Angeles: Sage Publications Inc.; 2017. p. 84–5. Scale; GFR: Glomerular Filtration Rate; HRQoL: Health Related Quality of Life; 3. 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